Cross-Species Alleviation of Biotic and Abiotic Stresses by the Endophyte Pseudomonas aeruginosa PW09

A wheat endophytic bacterium (Pseudomonas aeruginosa PW09) was evaluated for its ability to trigger an induced systemic resistance response in cucumber against biotic and abiotic stresses. PW09 was applied to cucumber seeds, and the seedlings were subjected to Sclerotium rolfsii infection and NaCl (150 mm). The role of PW09 was evaluated in alleviating the stresses by assessing plant mortality due to S.rolfsii infection and biomass accumulation under NaCl stress as well as at the physiological level through phenylpropanoid metabolism, antioxidant activities and proline accumulation. The endophyte reduced seedling mortality by 60% and increased biomass accumulation significantly under S.rolfsii (7%) and NaCl (18%) stresses, respectively, compared with endophyte-untreated seedlings. Application of PW09 also induced higher accumulation of proline (1.3- and 1.4-fold) and total phenolics (1.2- and 1.1-fold) and activities of polyphenol oxidase (4.3- and 1.5-fold), phenylalanine ammonia lyase (1.29- and 1.27-fold) and superoxide dismutase (2.5- and 1.39-fold) under S.rolfsii and NaCl stresses, indicating the ability of the wheat endophyte PW09 in alleviating both biotic and abiotic stresses in cucumber.